uutils coreutils Missing TOCTOU Protection on Non-Linux Unix Platforms in Safe Traversal Module

The safe_traversal module in uutils coreutils, which provides protection against Time-of-Check to Time-of-Use (TOCTOU) symlink races using file-descriptor-relative syscalls, is incorrectly limited to Linux targets. On other Unix-like systems such as macOS and FreeBSD, the utility fails to utilize these protections, leaving directory traversal operations vulnerable to symlink race conditions.